System and method for D2D resource allocation

ABSTRACT

When at least one of device-to-device UEs in connections of a group of D2D UEs is outside of the coverage area of mobile network of an access point, an information exchange mechanism established directly between the D2D UEs, without involving a third party, is provided. A resource allocation method for a device-to-device (D2D) communication link between two or more D2D user equipments (UEs) in a mobile communication network is provided according to an example. The method includes a first D2D UE indicating resource allocation information for the D2D communication link in a resource allocation message, wherein the resource allocation message is mapped into a resource allocation format; wherein the resource allocation format comprises one or more format flags; wherein one or more resource allocation messages are differentiated in the resource allocation format in accordance to the one or more format flags; and the first D2D UE transmitting the resource allocation format in a Physical Sidelink Control Channel (PSCCH) to one or more additional D2D UEs.

This application claims the benefit of U.S. Provisional Application No.62/045,465, filed on Sep. 3, 2014, entitled “Control information forD2D” which application is hereby incorporated herein by reference.

TECHNICAL FIELD

The present invention relates to a system and method for mobilecommunication network, and, in particular embodiments, to a system andmethod for device-to-device (D2D) direct connections.

BACKGROUND

In the field of mobile networks, especially in the radio accessnetworks, there has been increasing demand for heterogeneous networks,where different types of access points and mobile devices communicatewith each other. In addition, direct device-to-device (D2D)communication may be used to further boost the network capacity. D2Dcommunication refers to a communication mode between two or more userequipments (UEs) that does not include, or does not always include, anaccess point (AP) in a communication path between or among the UEs. D2Dcommunication is also called proximity service (ProSe) communication.Proximity service identifies a UE that is in proximity of another UE.

In a communication network where different types of communication linksshare a communication resource, they may undesirably interfere with eachother. For example, when D2D UEs and one or more non-D2D UEs share anuplink band during communications with a Base Transceiver Station (BTS),the D2D UEs and the cellular UE may interfere with each other.

SUMMARY

A method for communicating a resource allocation for a device-to-device(D2D) communication link between two or more D2D user equipments (UEs)in a mobile communication network is provided according to an example.The method includes a first D2D UE indicating resource allocationinformation for the D2D communication link in a resource allocationmessage, wherein the resource allocation message is mapped into aresource allocation format; wherein the resource allocation formatcomprises one or more format flags; wherein one or more resourceallocation messages are differentiated in the resource allocation formatin accordance to the one or more format flags; and the first D2D UEtransmitting the resource allocation format in a Physical SidelinkControl Channel (PSCCH) to one or more additional D2D UEs.

A device-to-device (D2D) UE is provided according to another example.The D2D UE includes a memory storing instructions; and a processorcoupled to the memory, wherein when the instructions are executed by theprocessor, the D2D UE is configured to indicate resource allocationinformation for a D2D communication link between the D2D UE and one ormore additional D2D UEs in a resource allocation message, wherein theresource allocation message is mapped into a resource allocation format;wherein the resource allocation format comprises one or more formatflags; wherein one or more resource allocation messages aredifferentiated in the resource allocation format in accordance to theone or more format flags; and transmit the resource allocation format ina Physical Sidelink Control Channel (PSCCH) to one or more additionalD2D UEs.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present invention, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings.

FIG. 1 shows a prior art D2D communication in a mobile communicationnetwork.

FIG. 2 shows a prior art D2D communication link resource allocation.

FIG. 3 shows an example of D2D communication in partial mobile networkcoverage.

FIG. 4 shows an example of D2D communication where all UEs are outsideof network coverage.

FIG. 5 shows an example of D2D link resource allocation.

FIG. 6 shows another example of D2D link resource allocation.

FIG. 7 shows an example of message flow in a D2D link connectionestablishment.

FIG. 8 shows resource pools for a D2D communication link.

FIG. 9 shows a computing platform that may be used for implementing, forexample, the devices and methods described herein, in accordance withany embodiment.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The structure, manufacture and use of the presently preferredembodiments are discussed in detail below. It should be appreciated,however, that the present invention provides many applicable inventiveconcepts that can be embodied in a wide variety of specific contexts.The specific embodiments discussed are merely illustrative of specificways to make and use the invention, and do not limit the scope of theinvention.

The terms used in this application, like “UE” or “device” or “terminal”as D2D devices can also comprise a subscriber, subscriber unit, asubscriber station, a mobile device such as a phone or tablet, a remotestation, a mobile station, a system, a remote terminal, an accessterminal, a user terminal, a user entity or user equipment (UE), acommunication device, a user agent, a user device, a laptop computer, ane-book reader or other devices. The term “UE” in the application alsorepresents a computer-related entity, such as but not limited tohardware, firmware, a combination of hardware and software, or softwarein execution. The disclosed embodiments also apply to machine-to-machine(M2M) communications. The devices disclosed herein can also mean suchkind of machines, like cars, buses, printers, copiers, refrigeratorsetc.

An access point (AP) can be, for example, a network controller, anevolved NodeB (eNB), a NodeB, a base station, a controller, a relay, arelay node and the like. According to the transmission power andbackhaul capability, the access point may also be known as a macro cell,low power node (LPN), relay node, pico cell, and so on.

A D2D communication link is a direct communication between two devices.The direct communication link can be called a D2D link, a proximityservice (ProSe) link, a sidelink, or other applicable term. The D2D linkwill facilitate interoperability between critical public safety networksand ubiquitous commercial networks because of an ability to offer newservices, improve system throughput, and offer a better user experience.

In D2D technology, there are two main operational phases: one isdiscovery, and the other is communication. Regarding the discovery phaseof a D2D device, for example, a UE can attempt to discover neighboringUEs. However, the discovery operation can be carried out by either theUE or the associated AP. Regarding the communication phase among D2Ddevices, for example, a UE directly communicates with another UE withoutthe data transiting through the AP.

FIG. 1 shows a prior art D2D communication in a mobile communicationnetwork 100. The mobile communication network 100 includes an AccessPoint (AP) 106, where the AP 106 generates a coverage area (dashedline). One or more user equipments (UEs) 102 and 104 can communicatewith the AP 106 and the mobile communication network 100. A first UE 102can transmit communication messages to a second UE 104 through the AP106. Alternatively, the first UE 102 can communicate with the second UE104 in a device-to-device (D2D) communications. In D2D, datacommunications are directly exchanged between participating D2D UEs.Control communications may be directly exchanged or may be relayedthrough the AP 106.

An access point (AP) 106 schedules the resources used by a first D2D UE102 to exchange data and control information with another D2D UE 104.The AP 106 controls transmission power of a scheduling assignment (SA)and data communications for the UE 102, 104, using the physical downlinkcontrol channel (PDCCH) or enhanced PDCCH (EPDCCH). Both the D2D UE 102and the D2D UE 104 are within range of the AP 106 in this example. Thetransmitting D2D UE 102, 104 transmits the resource allocationinformation to the receiving D2D UE 102, 104.

FIG. 2 shows a prior art D2D link resource allocation. A resource block204 is allocated from a sub-frame 202 of a frame 200 for a D2Dconnection. The D2D connection uses the allocated D2D resource 204 forboth control information 2062 and data transmission 2064 in a samechannel 206.

But when at least one of the D2D UEs is outside of the coverage area ofthe AP 106, the mobile communication network 100 cannot be used forexchanging resource allocation information. An information exchangemechanism established directly between the D2D UEs, without involving athird party, is thus needed.

In the embodiments, one transmitting D2D UE linking to and communicatingwith one receiving D2D UE is given as an example. However, more than twoD2D UEs can be involved in D2D communications, including one to one(D2D), device-to-multi-device (D2MD), or multi-device to multi-device(MD2MD). The D2D communication link shown below also applies toconnections between multiple D2D UEs.

FIG. 3 shows an example of D2D communication in partial mobile networkcoverage. When at least one D2D UE is outside of the coverage area 300of the AP 306, a D2D UE 302, 304 on its own selects resources fromresource pools to transmit direct data and control information. A D2D UE302, 304 can also use a resource that has been allocated by an accesspoint for D2D connections. The AP 306 generally does not participate inthe resulting D2D communication message transmissions. Both a receivingD2D UE and a transmitting D2D UE normally need to know the allocatedresources in order to establish connections between them.

In an embodiment, a resource allocation method for establishing adevice-to-device (D2D) communications link between two or more D2D userequipments (UEs) in a mobile communication network includes a first D2DUE indicating resource allocation information for the D2D communicationlink in a resource allocation message, wherein the resource allocationmessage is mapped into a resource allocation format; wherein theresource allocation format comprises one or more format flags; whereinone or more resource allocation messages are differentiated in theresource allocation format in accordance to the one or more formatflags; and the first D2D UE transmitting the resource allocation formatin a Physical Sidelink Control Channel (PSCCH) to one or more additionalD2D UEs.

The resource allocation format may include only one format flag, and theonly one format flag is mapped to all resource allocation messagesneeded for the communicating the resource allocation for the D2Dcommunication link.

The method may further include a dedicated control channel establishedbetween the first D2D UE and the one or more additional D2D UEsaccording to the resource allocation information, wherein the dedicatedcontrol channel is used for communicating only control informationbetween the first D2D UE and the one or more additional D2D UEs.

The resource allocation message may include one or more Sidelink ControlInformation (SCI) messages, and the one or more SCI messages are encodedaccording to the resource allocation format. Here encoding means the oneor more SCI messages are communicated in the resource allocation format.

Typically, a message is conveyed using a format selected from a set offormats. Generally a format is a container for a Sidelink ControlInformation (SCI) message. One or more formats may have a common size.Size of a format may comprise a number of information elements of theformat, or bits of the format, or resource blocks of the format. Aformat may also comprise a format flag. A format flag is used toindicate which type of SCI message is conveyed in a format. The formatflag can be used to distinguish the SCI message because one or more SCImessages can use a common format. In some examples, size of the formatflag is at least as large as the ceiling of the logarithm base 2 of thenumber of SCI messages supported by the format. If the size of the oneor more messages is less than a predetermined format length, then atleast one dummy bit is appended to the one or more message until the oneor more message length equals the predetermined format length.

The predetermined format length can be a size of the longest resourceallocation message among the one or more resource allocation messages.Then at least one dummy bit is appended to the other one or moreresource allocation messages until the size of the other one or moreresource allocation messages equals that of the longest resourceallocation message. In other words, at least one dummy bit can beappended to the existing one or more resource allocation messages untilthe size of the one or more resource allocation messages equal apredetermined size of a format. By doing so, the size of the one or moreresource allocation messages for each UE can be kept the same.Optionally, the dummy bit can be zero. In another alternative, theappending bit(s) is unspecified and ignored or not used by the D2D UE.

Optionally, all resource information needed for connections for the D2Dlink can be assigned to only one format. The one format contains allresource information that is needed for connections of D2D link. Allresource information can be indicated in information bits of the oneformat. Individual information bits of the one format can be mapped todifferent resource allocation information. The one format is carried inthe communication message to destination UEs.

For D2D communications, the number of PRBs used is unknown to thereceiving D2D UE. As a result, it is difficult to multiplex controlinformation with data information. The control information istransmitted separately from the data information by the transmitting D2DUE. The encoded bits of data information are interleaved and mapped to atransport channel, for example, the Physical Sidelink Shared Channel,PSSCH. The encoded bits of control information are interleaved andmapped to other transport channel, for example, the Physical SidelinkControl Channel, PSCCH.

More examples of possible solutions are illustrated below. Theseexamples can be either combined with the method or by themselvesindependently to provide solutions for D2D connections.

FIG. 4 shows an example of D2D communication where all UEs are outsideof network coverage. For an example, each pair of D2D UEs has adedicated control channel. A first D2D UE 402 can establish more thanone D2D communication link with the other D2D UEs 404, 406. The numberof D2D communication links that can be established at the same timedepends on how many resource blocks have been preconfigured for D2Dcommunications.

The control channel, for example, employs a Physical Sidelink ControlChannel (PSCCH) in some embodiments. The resources allocated for the D2Dcommunication link are typically allocated on the uplink portion of aframe, in an uplink band of the mobile communication network.

The control channel can be provided in many ways. For example at leastone resource block of a subframe is allocated for a PSCCH. The subframeis one of the subframes of an uplink frame.

FIG. 5 shows an example of D2D communication link resource allocation. Anumber of symbols is defined for a frame 500 which has a number ofsub-frames. The sub-frame has a number of channels which carry datainformation or control information. Channels are mapped to resourceblocks and a subframe includes a number of resource blocks. A D2Dallocation resource for a control channel is separate from the D2Dallocation resource for data transmission channel.

In an example, all resource blocks of a selected sub-frame in the frame500 can formulate a scheduling assignment (SA) pool, for examplesub-frame 504, sub-frame 506. A resource block can be selectedautonomously from the SA pool. In that way, a SCI format can betransmitted by the source UE in an autonomous manner, which means thetransmission does not need to be triggered by the AP. Alternatively, aseparate or dedicated pool for transmitting SCI format may be set up,for example, a subset of the existing SA pool.

A resource block can also be allocated by the source D2D UE byindicating a frequency and sub-frame to be used. By doing so, the SCIformat can be sent either in the SA pool or a separate pool.

The resource block can also be derived from the data frequency resourceallocation. For example, the first sub-frame in the SA pool can be asub-frame index. The lowest physical resource blocks (PRB) index of thereceived data frequency can be reserved for D2D communication linkresource allocation.

The resource allocation information is indicated in a resourceallocation message. The message can be a Sidelink Control Information(SCI) message. The Sidelink Control Information (SCI) messages are usedon the PSCCH to carry resource allocation information. A sidelink isused for ProSe direct communication and ProSe direct discovery betweenUEs.

In order to define content carried by the SCI format, or to definedifferent type of messages carried by the SCI format, SCI messages cancarry further information that is used by connections. For example atleast one format flag matching certain information of a resourceallocation is carried in the message. There can be a matching table forthe format flag matching which kind of certain resource allocationinformation. Thus, which information the format flag represents or whichinformation is carried in the SCI message would be parsed out. The SCIformat may comprise a field for the format flag.

The certain information that is carried by SCI messages includes atleast one of the following: scheduling of PSCCH for broadcast,scheduling of PSCCH for broadcast and/or unicast, unicast or multicastscheduling of PSSCH, or transmitting of feedback information. Thefeedback information may also include information such as a HybridAutomatic Retransmission reQuest (HARQ) acknowledgement (ACK) ornegative acknowledgement, which can be described in short form asacknowledgement and negative acknowledgement (ACK/NAK), or Channelcontrol quality information (CQI), etc. For example, SCI messages cancarry the above-mentioned types of information by matching differentformats or types of messages with at least one format flag.

FIG. 6 shows another example of D2D communication link resourceallocation. A subframe 600 represents a scheduling assignment (SA) poolwhich has a number of resource blocks. A D2D allocation resource forcontrol channel 606, 608 is separate from the resource for datatransmission 602, 604. One or more resource blocks can be reserved orassigned as a control channel 606, 608 to the same or different D2D UEs.One or more resource blocks are assigned as a data channel 602, 604 tothe same or different D2D UEs.

FIG. 7 shows an example of message flow in a D2D communication linkconnection establishment. The example is employed to establishconnections between D2D UEs 701, 703, 705 when at least a second D2D UE705 to be connected is out of the range of an access point (AP). In step710, a first D2D UE 701 transmits a communication message includingresource allocation information through a dedicated control channel tothe at least second D2D UEs 703, 705. The message is a SCI message insome embodiments. The communication message carries one or more formats.The one or more formats are mapped to certain control information of theresource allocation information. The first D2D UE 701 transmitsinformation on the control channel to the at least one of the other D2DUEs 703, 705 according to the resource allocation information. In step720, the at least second D2D UEs 703, 705 transmit information to thefirst D2D UE 701 on the dedicated control channel of each pair of D2DUEs 701, 703, 705 according to the resource allocation information.

The control information of resource allocation includes at least one ofthe following: scheduling of the control channel for broadcast,scheduling of the control channel for unicast, scheduling of the controlchannel for both broadcast and unicast, or transmitting of feedbackinformation.

The one or more formats can be used to convey SCI messages. An exampleof defined SCI formats is listed in Table 1. Not all of the formats needto be defined and present at the same time, in order to reduce thenumber of new formats to be defined or transmitted.

TABLE 1 Example of defined SCI formats Format Description 0 Used for thescheduling of Physical Sidelink Shared Channel (PSCCH) for broadcast0-ext Used for the scheduling of release-12 PSCCH for broadcast andunicast (SCI format-0 appended) 1 Used for feedback and may include infosuch as HARQ acknowledgement/negative acknowledgement (ACK/NAK), CQI,etc. 2 Used for unicast or multicast scheduling of release-x (x > 12)PSSCH, for future definition

FIG. 8 shows resource pools for a D2D communication link. FIG. 8 showsan example uplink frame with ten subframes labeled 0 to 9. Subframe 1has a pool of resource blocks allocated for the PSCCH on the sidelink.Subframe 5 has a pool of resource blocks allocated for the PSSCH on thesidelink.

For example, SCI format 0 is configured for the scheduling of PSSCH. Theprocedure can comprise the following. SCI format 0 is used to transmitthe information below, such as how many bits of the message are used forcarrying the respective information (shown as an example in thebrackets).

-   -   Frequency hopping flag (1 bit).    -   Resource block assignment and hopping resource        allocation—┌log₂(N_(RB) ^(SL)(N_(RB) ^(SL)+1)/2)┐ bits.        -   For PSSCH hopping:            -   N_(SL) _(_) _(hop) MSB bits are used to obtain the value                of ñ_(PRB)(i)            -   (┌log₂(N_(RB) ^(SL)(N_(RB) ^(SL)+1)/2)┐−N_(SL) _(_)                _(hop)) bits provide the resource allocation of the                first slot in the subframe.        -   For non-hopping PSSCH:            -   (┌log₂(N_(RB) ^(SL)(N_(RB) ^(SL)+1)/2┐) bits provide the                resource allocation in the subframe.    -   The Time-Resource Pattern Transmission (T-RPT) is the indication        of the subframes for the D2D resource allocation, T-RPT index (7        bits).    -   Modulation and coding scheme and redundancy version (5 bits)    -   Timing advance indication (5 bits)

Note that N_(RB) ^(SL) is the sidelink bandwidth configuration expressedin the number of resource blocks (RBs).

For example, two or more SCI formats are carried in a SCI message. TheSCI message can use a format flag or a flag field to identify suchformat. For example, SCI format 0-ext can carry such a format flag. Thefields of the SCI formats may be different depending on the value of theformat flag. Alternatively, the fields of one SCI format may comprise asubset of some or all of the fields of another SCI format. For example,the SCI corresponding to the format flag with value 0 may be scheduledfor broadcast communication. A UE may ignore or discard an SCI receivedwith a format flag with value 1. Another UE may be able to understandSCI with format flag with value 0 or value 1. When a SCI format has aformat flag, the value of the format flag can determine how to interpretthe bits or fields of a message. If the value of the format flag is 1,the fields of the SCI could comprise some or all of the fields of theSCI with a format flag of 0. Some new fields may be present, or somefields from the SCI with format flag 0 may be renamed or have a newmeaning if the format flag is 1. The size of format 0-ext would have tobe the larger one of the information needed to be contained in format 0and format 1. Fields of extra information bits may need to be added toone or more of the formats so that the total size is the same for allformats.

Alternatively, a format flag can reserve at least one information bit tobe added additional SCI types in the future.

A resource allocation type indicates if the SCI carries a SCI format 0assignment (as described above) or the format 0-ext assignment or otherSCI format assignments. Alternatively, a resource allocation type isassigned to indicate which format flag is carried by the SCI message.

If the resource allocation type is set to 0, the format carries a SCIformat 0, and the fields may be set as above described example. If theresource allocation type is set to 1, the format carries a SCI format0-ext. For example SCI format 0-ext is used to transmit belowinformation, and how many bits of the sub-frame are used for carryingthe respective control information is shown as an example in thebrackets:

-   -   1. Frequency hopping flag (1 bit).    -   2. Resource blocks assignment and hopping resource allocation        ┌log₂(N_(RB) ^(SL)(N_(RB) ^(SL)+1)/2)┐ bits. This field is        encoded similarly to what is done in Downlink Control        Information (DCI) format 0 for resource allocation type 0 (with        or without hopping) and resource allocation type-1.    -   3. Time resource assignment, this field indicates which        subframes comprise the resource allocation. It may be encoded        similarly to e.g., a T-RPT, as described in the previous        section.    -   4. Modulation and coding scheme and redundancy version (5 bits).

Note that N_(RB) ^(SL) is sidelink bandwidth configuration expressed innumber of resource blocks.

For example, SCI format 1 is used by the D2D UE corresponding to thedestination ID to transmit feedback information to the D2D UEcorresponding to the source ID.

Note that all the fields may not need to be present all the time. Thiscan also be useful if format 1 can be transmit either when triggered bythe source ID, or not triggered.

Note that some of this information may be encoded without having aspecific field. For instance, the ID may be used to scramble the CyclicRedundancy Check, CRC.

In an example, SCI format 2 is used for the scheduling of PSSCH forbroadcast/multicast/unicast communication.

In an example, fields of the SCI format 2 are used to transmit theinformation below, such as how many bits of the sub-frame are used forcarrying the respective information (shown in the brackets).

-   -   1. Frequency hopping flag (1 bit).    -   2. Resource block assignment and hopping resource allocation        (┌log₂(N_(RB) ^(SL)(N_(RB) ^(SL)+1)/2)┐ bits). This field is        encoded similarly to what is done in DCI format 0 for resource        allocation type 0 (with or without hopping) and resource        allocation type-1.    -   3. Time resource assignment: this field indicates which        subframes comprise the resource allocation. It may be encoded        similarly to e.g., an T-RPT, as described in the previous        section.    -   4. Modulation and coding scheme and redundancy version (5 bits).

Note that N_(RB) ^(SL) is the sidelink bandwidth configuration expressedin number of resource blocks.

In encoding the SCI, a D2D UE may need to transmit more than oneformats, for example, an SCI format 0, an SCI format 1, or a combinationof two or more formats. For example for bi-directional, symmetriccommunication, a combination of two or more formats might be needed. Asingle, long container is defined with one or more format flags toindicate the content that is in the container. The content means theformat flags and the control information details that the format aremapped to. The unused bits of the format can be appended or filled orpadded in with zeroes. The length means the size of payload of theformat. Thus, having a communication message of variable size isavoided. The one or more formats can also be one format which combinesall resource control information needed for connections for the D2Dcommunication link.

Alternatively, SCI formats may be distinguished by the resources thatthe SCI are transmitted, for example, different resource pools.

By the above described solutions, the decoding D2D UE receives the sizeof the format as expected. The decoding side does not need to do blinddecoding when decoding the SCI message.

An example for encoding a SCI message is to assign a D2D resourceallocation (DRA) type. One SCI format is corresponded to one DRA type.The DRA type is signaled by the AP, or one of the D2D UEs in theconnections. The DRA type can be transmitted using Radio ResourceControl (RRC) signaling. The correspondence between DRA and SCI formatcan be as indicated in exemplary Table 2.

TABLE 2 DRA SCI format 0 0 1 2, no MIMO 2 2, open-loop MIMO Etc. Etc.

Another embodiment is provided. A device-to-device (D2D) UE includes anindicator component that indicates resource allocation information for aD2D communication link in a resource allocation message; a mappingcomponent that maps the resource allocation message into a resourceallocation format, wherein the resource allocation format comprises oneor more format flags; an encoder component that differentiates one ormore resource allocation messages in the resource allocation format inaccordance to the one or more format flags; and a transmitter thattransmits the resource allocation format in a Physical Sidelink controlChannel (PSCCH) to one or more additional D2D UEs.

FIG. 9 shows a computing platform 1100 that may be used forimplementing, for example, the devices and methods described herein, inaccordance with any embodiment. Specific devices may utilize all of thecomponents shown, or only a subset of the components, and levels ofintegration may vary from device to device. Furthermore, a device maycontain multiple instances of a component, such as multiple processingunits, processors, memories, transmitters, receivers, etc. Theprocessing system 1101 in the embodiment shown comprises a processingunit equipped with one or more input/output devices, such as a speaker,microphone, mouse, touchscreen, keypad, keyboard, printer, display, andthe like (not shown). The processing unit 1100 may include a centralprocessing unit (CPU) 1110, memory 1120, a mass storage device 1130, andan I/O interface 1160, connected to a bus 1140.

The bus 1140 may be one or more of any type of several bus architecturesincluding a memory bus or memory controller, a peripheral bus, videobus, or the like. The CPU 1110 may comprise any type of electronic dataprocessor. The memory 1120 may comprise any type of non-transitorysystem memory such as static random access memory (SRAM), dynamic randomaccess memory (DRAM), synchronous DRAM (SDRAM), read-only memory (ROM),a combination thereof, or the like. In an embodiment, the memory 1120may include ROM for use at boot-up, and DRAM for program and datastorage for use while executing programs.

The mass storage 1130 may comprise any type of non-transitory storagedevice configured to store data, programs, and other information and tomake the data, programs, and other information accessible via the bus.The mass storage 1130 may comprise, for example, one or more of a solidstate drive, hard disk drive, a magnetic disk drive, an optical diskdrive, or the like.

The I/O interface 1160 couples external input and output devices to theprocessing unit 1100. As illustrated, examples of input and outputdevices include a display and a mouse/keyboard/printer (not shown)coupled to the I/O interface 1160. Other devices may be coupled to theprocessing unit 1100, and additional or fewer interface devices may beutilized. For example, a serial interface such as Universal Serial Bus(USB) (not shown) may be used to provide an interface for a printer.

The processing unit also includes one or more network interfaces 1150,which may comprise wired links, such as an Ethernet cable or the like,and/or wireless links to access nodes or different networks 1180. Thenetwork interface 1150 allows the processing unit to communicate withremote units via the network 1180. For example, the network interface1150 may provide wireless communication via one or moretransmitters/transmit antennas 1170 and one or more receivers/receiveantennas. In an embodiment, the processing unit is coupled to alocal-area network or a wide-area network for data processing andcommunications with remote devices, such as other processing units, theInternet, remote storage facilities, or the like.

For example, a device-to-device (D2D) UE includes a memory that storesinstructions and a processor coupled to the memory. When theinstructions are executed by the processor, a D2D UE indicates resourceallocation information for the D2D communications link, indicateresource allocation information for a D2D communication link between theD2D UE and one or more additional D2D UEs in a resource allocationmessage, wherein the resource allocation message is mapped into aresource allocation format; wherein the resource allocation formatcomprises one or more format flags; wherein one or more resourceallocation messages are differentiated in the resource allocation formatin accordance to the one or more format flags; and transmit the resourceallocation format in a Physical Sidelink Control Channel (PSCCH) to oneor more additional D2D UEs.

The following references are related to subject matter of the presentapplication. Each of these references is incorporated herein byreference in its entirety:

-   -   3GPP TS 36.212 Specification v12.1.0 (Jul. 3, 2014).    -   3GPP TS 36.213 Specification v12.2.0 (Jul. 3, 2014).    -   3GPP TS 36.331 Specification v12.2.0 (Jul. 4, 2014).

While this invention has been described with reference to illustrativeembodiments, this description is not intended to be construed in alimiting sense. Various modifications and combinations of theillustrative embodiments, as well as other embodiments of the invention,will be apparent to persons skilled in the art upon reference to thedescription. It is therefore intended that the appended claims encompassany such modifications or embodiments.

Abbreviations are provided below: AP Access point BCH Broadcast CHannelBTS Base Transceiver Station CFI Control Format Indicator CP CyclicPrefix CQI Channel Quality Control Information CRC Cyclic RedundancyCheck CSI Channel State Information DCI Downlink Control InformationDL-SCH Downlink Shared CHannel DRA D2D Resource Allocation eNB evolvedNodeB EPDCCH Enhanced Physical Downlink Control CHannel FDD FrequencyDivision Duplexing HARQ Hybrid Automatic Retransmission Request HI HARQIndicator MCH Multicast CHannel M2M Machine-to-Machine PBCH PhysicalBroadcast CHannel PCFICH Physical Control Format Indicator CHannel PCHPaging CHannel PDCCH Physical Downlink Control CHannel PDSCH PhysicalDownlink Shared CHannel PHICH Physical HARQ Indicator CHannel PMCHPhysical Multicast CHannel PMI Precoding Matrix Indicator PRACH PhysicalRandom Access CHannel PRB Physical Resource Blocks ProSe ProximityService PSBCH Physical Sidelink Broadcast CHannel PSCCH PhysicalSidelink Control CHannel PSDCH Physical Sidelink Discovery CHannel PSSCHPhysical Sidelink Shared CHannel PUCCH Physical Uplink Control CHannelPUSCH Physical Uplink Shared CHannel RACH Random Access CHannel RBResource Block RI Rank Indication RRC Radio Resource Control SAScheduling Assignment SCI Sidelink Control Information SL-BCH SidelinkBroadcast CHannel SL-DCH Sidelink Discovery CHannel SL-SCH SidelinkShared CHannel SR Scheduling Request SRS Sounding Reference Signal TDDTime Division Duplexing TPMI Transmitted Precoding Matrix Indicator UCIUplink Control Information UE User Equipment UL-SCH Uplink SharedCHannel

What is claimed is:
 1. A method for communicating a resource allocationfor a device-to-device (D2D) communication link between two or more userequipments (UEs) in a mobile communication network, the methodcomprising: identifying one or more Sidelink Control Information (SCI)message types each having a respective resource allocation format,wherein each message type comprises one or more format flags indicatingthe respective resource allocation format; for each of the SCI messagetypes, determining a length of a longest message of that type, obtaininga first SCI message having a first type; adjusting a length of the firstSCI message based on the determined length of the longest SCI message ofthe first type; and transmitting the adjusted first SCI message by afirst UE in a Physical Sidelink Control Channel (PSCCH) to one or moresecond UEs for establishing the D2D communication link.
 2. The method ofclaim 1, wherein the resource allocation format comprises only oneformat flag, and the only one format flag is mapped to all messagestypes needed for the communicating the resource allocation for the D2Dcommunication link.
 3. The method of claim 1, further comprising:establishing, by the first UE, a dedicated control channel between thefirst UE and the one or more second UEs according to the resourceallocation information, wherein the dedicated control channel is usedfor communicating only control information between the first UE and theone or more second UEs.
 4. The method of claim 1, wherein the one ormore SCI messages are encoded according to the respective resourceallocation format.
 5. The method of claim 1, further comprising:determining that the length of the first SCI message is less than thepredetermined length of the longest SCI message of the first type and,based thereon, appending one or more dummy bits to the first SCI so thatthe size of the first SCI equals the length of the longest message ofthe first type.
 6. The method of claim 5, wherein the dummy bit is zero.7. The method of claim 1, further comprising: transmitting, in the firstSCI message, sidelink scheduling information for one destination ID ofthe one or more second UEs.
 8. The method of claim 1, wherein theresource allocation format is at least one of the following, format 0,format 1, format 2 or format 0-ext.
 9. The method of claim 1, wherein anSCI message comprises resource allocation information which is at leastone of the following, scheduling of the share channel for broadcast,scheduling of the share channel for unicast, scheduling of the sharechannel for both broadcast and unicast, or transmitting of feedbackinformation.
 10. The method of claim 1, further comprising: allocatingat least one resource block of a sub-frame for transmitting the firstSCI message to the one or more second UEs, wherein the sub-frame is asub-frame of an uplink frame.
 11. A device-to-device (D2D) userequipment (UE) comprising: a memory storing instructions; and aprocessor coupled to the memory, wherein when the instructions areexecuted by the processor, the UE is configured to: identify one or moreSidelink Control Information (SCI) message types each having arespective resource allocation format, wherein each message typecomprises one or more format flags indicating the respective resourceallocation format; for each of the SCI message types, determine a lengthof a longest message of that type, obtain a first SCI message having afirst type; adjust a length of the first SCI message based on thedetermined length of the longest SCI message of the first type; andtransmit the adjusted first SCI message by a first UE in a PhysicalSidelink Control Channel (PSCCH) to one or more second UEs forestablishing the D2D communication link.
 12. The D2D UE of claim 11,wherein the resource allocation format comprises only one format flag,and the only one format flag is mapped to all resource allocationmessages types needed for the communicating the resource allocation forthe D2D communication link.
 13. The D2D UE of claim 11 furtherconfigured to: establish by the first UE, a dedicated control channelbetween the first UE and the one or more second UEs according toresource allocation information, wherein the dedicated control channelis used for communicating only control information between the first UEand the one or more second UEs.
 14. The D2D UE of claim 11, wherein theone or more SCI messages are encoded according to the respectiveresource allocation format; and determining that the length of the firstSCI message is less than the predetermined length of the longest SCImessage of the first type and, based thereon, appending one or moredummy bits to the first SCI so that the size of the first SCI equals thelength of the longest message of the first type.
 15. The D2D UE of claim14, wherein the dummy bit is zero.
 16. The D2D UE of claim 11, whereinin the first SCI message transmits sidelink scheduling information forone destination ID of the one or more second UEs.
 17. The D2D UE ofclaim 11, wherein the the first UE is further configured to allocate atleast one resource block of a sub-frame for transmitting the first SCImessage to the one or more second UEs, wherein the sub-frame is asub-frame of an uplink frame.